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Патент USA US3057263

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Oct. 9, 1962
c. P. JOHNSON, JR
3,057,253
OPTICAL PYROMETER WITH PHOTOELECTRIC DETECTOR
Filed sept. 12, 1958
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INVENTOR.
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United States Patent Office
3,057,253
Patented Oct. 9, 1962
2
1
current fiow through filament 13, the correct amount of
3,057,253
OPTICAL PYROMETER WITH PHOTOELECTRIC
DETECTOR
C. Peter Johnson, Jr., Putnam Valley, N.Y.
Filed Sept. 12, 1958, Ser. No. 760,604
11 Claims. (Cl. Sii-22.5)
The present invention relates to optical pyrometers and
more particularly to a pyrometer of this type provided
current fiow having been previously determined by cali
bration techniques.
A second lens or optical system 18 is directed toward
the filament 13 and produces a real image (not shown)
consisting of the filament 13 with the object 10 as a back
ground, this image being produced at a second vertical
focal plane passing through the line 19. An opaque
screen member 20 lies in this second focal plane and has
with photoelectric means for optically comparing the bril 10 an observation slit 21 formed therein. The optical axes
of the lenses 11 and 18 are in alignment with each other
liance of a high temperature object with the brilliance of
and with the slit 21 and constitute the principal optical
an electrically heated incandescent filament which serves
as a temperature reference.
The pyrometer of the present invention is characterized
axis of the pyrometer.
The filament 13 also lies on this
principal optical axis.
by its simplicity and unusual precision of measurement.
An interference filter 22 having narrow pass band is
At temperatures of the order of 130‘0° C. it has an ac
curacy of a few tenths of one degree.
disposed on the principal optical axis of the instrument and
is interposed between the second lens 18 and the observa
tion slit 21. The characteristics of the filter 22 are 4such
Generally, the pyrometer comprises an objective lens
as to exclude light of wave lengths lying outside the range
which is directed toward an incandescent heated object
20 actually used for temperature measurements. The instru
having a high temperature which is to be measured.
A real image of the object is produced at a focal plane
which passes through the incandescent filament of a cali
ment is thus rendered substantially monochromatic in its
response characteristics.
brated reference temperature lamp. The combined image
Disposed between the filter 22 and the slit 21 is a scan
ning refractor 24 which is shown as a block of glass of
of the object and the filament is focused by a second opti
cal system at a second focal plane which contains an 25 square cross section rotatable about the axis 25 perpen
opaque surface having an observation slit formed therein.
A photoelectric tube of the photomultiplier tube is dis
posed behind the slit. A block of glass is interposed be
_tween the second optical system and the slit.
By rotat
ing the block of glass, which preferably has two parallel
dicular to the plane of the drawing and located at the
center of the square block. The rotational axis 25 inter
sects the principal optical axis of the instrument. The
glass block 24 has spaced fiat parallel optically finished
surfaces 27. The finished surfaces 27 are parallel to and
equidistant from the rotational axis 25. The other two
surfaces 28 need not be finished and may be made opaque,
optically finished fiat surfaces, the beam of light falling
on the slit is shifted laterally by refraction so that the
if desired. Alternatively all four faces may be optically
image of the object and the image of the filament may be
lcaused to pass through the slit separately at different 35 finished. Other forms of cross-sectional configuration
may be used so long as there are at least two optically
times. The photoelectric cell is connected through suit
finished surfaces between which light may pass and be
able amplifying means with a chart recorder. If the am
refracted for lateral displacement which varies in amount
plifier output remains constant during rotation of the block
by rotation of the glass block.
of glass, the filament and object are at the same brightness
The glass block 24 is connected by suitable driving
temperature and the chart record is a continuous straight 40
means indicated by a dotted line 29 to be rotated on its
line. If the two brightness temperatures are appreciably
axis 25 by a motor 30. With the faces 27 exactly verti
different, then a pip appears in the trace made by the pen
cal, a central ray of light 31 would pass along the principal
of the chart recorder, the amplitude of the pip being
optical axis of the instrument and enter the slit 21. How
greater for larger temperature differences.
Various objects, features and advantages of the inven 45 ever, with the faces 27 inclined with respect to the prin
cipal axis, as shown, the ray 31, instead of entering the
- tion will become apparent upon reading the following spec
slit 21 is refracted so that it emerges from the glass block
ification together with the accompanying drawing form
24 displaced from the principal axis as indicated at 31a.
ing a part thereof.
Since the central ray 31 is included in the filament image
Referring to the drawing:
FIGURE 1 is a diagrammatic illustration of an optical 50 portion of the combined image falling on screen member
pyrometer embodying the invention.
FIGURE 2 is a fragmentary view of a strip chart rec
20, in the position shown, the object portion of the com
bined image is entering the observation slit 21. Only
while the faces 27 are nearly perpendicular to the principal
axis does the filament portion of the combined image en
ord illustrating the visual indication produced by the
pyrometer.
Referring to FIG. l the incandescent object which is the 55 ter the slit 21.
Disposed behind the observation slit 21 is a phototube
subject of the temperature measurement is indicated at
of the photomultiplier type designated as 32. The photo
10. An objective lens or optical system 11 is directed to
tube 32 is so arranged that light passing through the slit
ward the object 10 and produces a real image (not shown)
of the object 10 which lies in a first vertical focal plane
2l falls on the most sensitive portion of the tube, the
passing through the line 12. The plane passing through 60 slit 21 lying on the principal optical axis of the instru
ment. The phototube 32 is connected to the input of an
the line 12 also passes through an incandescent filament
amplifier 33. The output of amplifier 33 is- connected
13. The filament 13 is disposed within an evacuated glass
to Va strip chart recorder in the form of a zero-center
envelope 14. The envelope 14 comprises optically fin
-recording millivoltmeter which produces a trace 35 (FIG.
ished -fiat glass walls 15 which are inclined with respect
to the vertical for diverting refiected light away from the 65 2) on a strip chart 36. The amplifier 33 contains` an ad
justable balancing circuit of conventional type such that
‘optical axis of the pyrometer.
therecorder 34 may be manually adjusted to Zero center
The filament 13 is energized by a source of electrical
-in response to the brilliance of light reaching the photo
,energy indicated as a battery 16. The battery 16 is con
tube 32 from the object portion of the image focused on
nected to the filament 13 through an adjustable rheostat
17. The filament 13 can be brought with precision to 70 the screen 20, or the brilliance of the filament 13, as
any desired predetermined temperature of incandescence
by adjusting the rheostat 17 to provide a corresponding
desired.
In operation, the glass block or prism 24 is rotated
3,057,253
by the motor 30‘, for example, at a speed of 3/15 revolu
tion per minute and with the strip chart 36 feeding at a
linear speed of 6 inches per minute. The rheostat 17 is
adjusted to provide a predetermined current ñow through
the filament 13 such that the brilliance of its incandes
cence corresponds accurately to the brilliance for the
desired temperature of object 10. The temperature of
object 10 is thereafter adjustedY so that the trace 35 is a
of said refracting member being parallel to said flat sur
faces, said refracting member directing the image of said
filament into said slit within a limited range of rota
tion thereof and onto said screen during a further range
of rotation whereby the imagel of said filament and the
image of said object fall on said slit separately for dif
ferent rotational posi-tions of said refracting member and
photoelectric detecting means disposed behind said slit.
3. A pyrometer according to claim 2, further com
smooth unbroken straight line. The temperatu-re of the
object 10 is then equal to the predetermined desired 10 prising a monochromatic filter means interposed between
temperature.
said objective lens means and said detecting means.
Alternatively, the amplifier 33 is adjusted so that the
4. A pyrometer according to claim 2, wherein said
trace 35 is centered on the chart 36, as shown. Rheostat
rotational axis lies midway between said fiat surf-aces,
17 is then 'adjusted so that the pips such as pips 37 are
eliminated. The temperature of the filament 13 is then
equal to the temperature of the object 10. For tempera
ture differences in the opposite direction, the pips 38 in
dicated in ydotted lines will be produced. When there are
no pips the Itemperatures are equal.
Although Ithe same comparisons may be made by ob 20
serving an indicating millivoltmeter without any record
ing chart, it must be watched closely and continuously
to ydetect whether there is any deiiection of the needle
when the filament portion of the image passes over the
observation slit 21. Because the temperature of the ob
said pyrometer further comprising drive means for con
tinuously rotating said block.
5. A pyrometer according to claim 4, wherein said
glass block is of rectangular cross-section and said fiat
surfaces ‘are `disposed at opposite sides of said rectangle,
the rotational axis of said block being disposed at the
center of said rectangle.
6. A pyrometer according to claim 2, wherein said
detecting means comprises a chart recorder producing a
trace having pips therein when the temperatures of said
filament and said object are unequal, said trace being a
continuous straight line when said temperatures are equal.
7. A pyrometer according to claim 2, wherein said
filament is disposed in an evacuated glass envelope hav
ing opposite optically finished walls which extend trans
ject 10, if it is a furnace, changes very slowly, it is de
sirable to’ use the strip chart recorder. The scanning
speed may be increased, if desired, when an indicating
instrument is used. The' slow speed described above,
versely of said aligned optical axes, said walls being
however, avoids errors which might be introduced by 30 inclined to divert reflected light away from said axes.
the inherent inertia and damping of the indica-ting and/
8. An optical pyrometer having a principal optical
or recording instrument.
axis, said pyrometer comprising objective lens means
It will be apparent to those skilled in the art that
having an optical axis which coincides with said prin
various modifi-cations may be made in the specific em
cipal axis, said objective lens means being adapted to
bodiment of the invention which is herein illustratively
be directed toward an incandescent object the tempera
shown and `described without departing from the spirit
ture of which is to be measured, said objective lens means
and sc-ope of the invention `as defined in the appended
producing a real image of said object at a ñrst focal
claims.
plane, an incandescent filament of adjustable tempera
What is claimed is:
ture disposed on said principal axis at said first focal
1. An optical pyrometer comprising objective lens 40 plane, second lens means having an optical axis which
means ladapted to be directed toward an incandescent
coincides with said principal axis, said second lens means
object the temperature of which is to be determined, said
producing a real image at a second focal plane, said
objective lens means producing a real image of said
image at said second focal plane being a combined image
object at a first predetermined plane, an incandescent
of said object and said filament, an opaque screen mem
filament disposed at said first plane, means for bringing
ber disposed at said second focal plane, said screen mem
said filament to a known temperature o-f incandescence, 45 ber having an observation slit formed therein through
second lens means producing a combined real image of
which said principal axis passes, a phototube disposed
said .object and said filament at a second predetermined
behind said slit, said principal axis passing through a
plane, an opaque screen member disposed at said sec
light sensitive portion of said phototube, detector means
ond plane, said screen member having an observation
connected to said phototube for response to changes in
slit formed therein, a movable refracting member dis 50 illumination falling on said light sensitive portion, a re
posed between said second lens means and said screen
voluble glass block having at least two spaced parallel
member, means for displacing said refracting member
optically finished surfaces which are parallel to and
to move said combined image with respect `to said slit
equidistant from the rotational axis of said block, said
whereby the filament and object portions of said com
rotational axis intersecting said principal axis, said glass
bined image pass 'through said slit separately and at 55 block being disposed between said second lense means
different times, and photoelectric detecting means dis
and said slit, and means for rotating said glass block to
posed behind said slit.
move said combined image with respect to said slit
2. An optical pyrometer comprising objective lens
whereby the filament and object portions of said image
pass through said slit separately and at different times.
9. A pyrometer according to claim 8, wherein said
object lthe temperature of which is t-o be determined, 60
last-named means comprises continuously operable drive
said objective lens means> producing a first -real image of
means connected to rotate said glass block whereby said
said object at a first focal plane, second lens means hav
combined image is repeatedly displaced in a cyclical
ing its optical axis in alignment with the optical axis of
means adapted to be directed toward an incandescent
said objective lens means, said second lens means pro 65 manner.
l0. A pyrometer according to claim 8, further com
ducing a real image of said first real image at a sec
prising monochromatic filter means interposed between
ond focal plane, an incandescent filament disposed in
said objective lens means and said phototube,
said first focal plane and |on said aligned yoptical axes
whereby an image of said filament is included in the
ll. An optical pyrometer comprising objective lens
image at said second focal plane, an opaque screen hav 70 means adapted to be directed toward an incandescent
object the temperature of which is to be determined,
ing an observation slit formed therein, said slit being
said objective lens means producing a real image of said
disposed at said second focal plane, a revoluble refract
object at a first predetermined plane, an incandescent
ing member consisting of a glass block having at least
filament disposed at said first plane, means for bringing
two optically finished spaced parallel fiat surfaces dis
said filament to a known temperature of incandescence,
posed at opposite sides of said block, the rotational axis 75 second lens means producing a combined real image of
8,057,253
5
said object and said ñlament at a second predetermined
plane, an opaque screen member disposed at said second
plane, said screen member having an observation slit
formed therein, a movable refracting member disposed
between said first and second planes, means for displac
ing said refracting member to move said combined image
with respect to said slit whereby the filament and object
portions of said combined image pass through said slit
separately and at different times, and photoelectric de
10
tecting means disposed behind said slit.
References Cited in the ñle of this patent
UNITED STATES PATENTS
1,561,583
Bash ________________ .__ NOV. 17, 1925
1,908,977
1,970,103
2,096,323
2,213,904
2,469,115
2,572,488
2,798,961
2,807,976
2,898,176
6
Gruss et al ____________ .__ May 16, 1933
Runaldue ____________ __ Aug. 14, 1934
Gille _________________ __ Oct. 19,
Dunn _______________ __ Sept. 3,
Jagersberger __________ __ May 3,
Jagersberger __________ __ Oct. 23,
1937
1940
1949
1951
Wormser _____________ __ July 9, 1957
Vossberg _____________ __ Oct. 1, 1957
McNaney ____________ __ Aug. 4, 1959
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